Influence of Ascorbic Acid, Gibberellic Acid and Moringa oleifera Extract for Alleviating Salinity Stress by Enhancing Antioxidant Enzymatic Activity and Some Physiological Studies on Two Tomato Cultivars

This study aimed to explain the influence of Ascorbic acid (ASA), Gibberellic Acid (GA3) and Moringa oleifera Leaf Extract (MLE) for alleviating salinity stress by enhancing antioxidant enzymatic activity as follow: Super Oxide Dismutase (SOD), Catalase (CAT), Ascorbate Peroxidase (APX), and Glutathione Reductase (GR); nitrogenous components (proline and total amino acids) and some inorganic mineral nutrient elements in two tomato cultivars, cv. Cobra (resistant) and cv. Newton (sensitive) under salinity stress. Germination tomato seeds after soaking in ASA (0.75 mM); GA3 (0.05 mM) and MLE (5%), transplanted to plastic containers containing a mixture of sand/peat-moss (1:2). The tomato seeds for both cultivars watering using distilled water until the true leaf appearance then irrigated with NaCl salinity concentrations (0.0, 50, 100, 150, 200 mM) alternative with Hoagland nutrient solution. The experiment was carried out under greenhouse conditions with temperature 18oC±1oC (night) & 22oC±2°C (day) and relative humidity varied between 60 - 70%. Overall, the results indicated that the organic and inorganic components in tomato plants for both cultivars increased significantly in the present of ASA, GA3 and MLE under salinity stress respectively compared with control, there by reduces the harmful effects of salinity and increases resistance to salinity stress more than in the absent of ASA, GA3 and MLE. The data provide strong support to the hypothesis that exogenous application of ASA, GA3 and MLE reduced the harmful effects of NaCl concentrations and increases resistance to salinity in cv. Cobra and cv. Newton respectively. The evident recorded a significantly increased the antioxidant enzymes activity, proline, total amino acids and inorganic macro-mineral nutrient elements (N+3, P+3, K+, Ca+2 & Mg+2) and micro-nutrient mineral elements (Mn+2, Fe+3 & B+2) but after soaked the seeds in ASA, GA3 and MLE, these components tended to increase more compared with the control. Whereas, the tomato seeds soaked before planting in ASA, GA3 and MLE which leads to remarkably increasing more for all antioxidant enzymatic activity, nitrogenous components and inorganic mineral nutrient elements contents respectively. The relationship between compatible solutes (osmolytes) here are the strategies that plants have developed to tolerate salt stress and produced new strains adapted to salinity stress.